1. Field of the Invention
The present invention relates to a piezoelectronic device and a method of fabricating the same and, more particularly, to a piezoelectronic device having carbon nanotubes covered with a piezoelectronic material and the method of fabricating the same.
2. Description of Related Art
Piezoelectronic effect is the ability of some materials to convert mechanical stress into electrical energy by generating an electric field or electric potential in response to applied mechanical stress. Piezoelectronic materials can be applied into numerous uses such as bio-medical usages, electrical vehicle, wind power plants, hydroelectric power plant, wireless sensors, personal electronics, micro-electro-mechanical systems (MEMS), nano-electro-mechanical systems (NEMS) etc. Materials exhibit piezoelectricity, including ceramics such as BaTiO3 (BT, barium titanate) or Pb(Zr0.53Ti0.47)O3 (PZT, lead zirconate-titanate), single crystals such as quartz, tourmaline, Rochelle salts, tantalates, niobates, aluminium nitride (AlN), gallium nitride (GaN), or zinc oxide (ZnO), etc. In order to output large amount of electricity, nano-sized piezoelectronic devices provides high specific surface area, therefore zinc oxide nanowires are produced to serve as the nano-scaled piezoelectronic material of the new generation piezoelectronic devices.
In this regard, a piezoelectronic material made of zinc oxide nanowires is proposed in US2008/0067618 for the manufacture of piezoelectronic devices. Reference with FIG. 1, a piezoelectronic device of prior arts comprises: a first conductive layer 11 (serves as a lower electrode) and a second conductive layer 12 (serves as an upper electrode); a plurality of zinc oxide nanotubes 13 locating between the first conductive layer 11 and the second conductive layer 12, in which one end of each of the zinc oxide nanotubes 13 connects with the first conductive layer 11. Therefore, when a mechanical strength is applied to the second conductive layer 12 to compress the zinc oxide nanotubes 13, an induced voltage or current is generated as well as a piezoelectronic effect due to the compression.
However, the induced current obtained from a conventional piezoelectronic device is only about 10−12 to 10−9 μA. And since the zinc oxide nanotubes are easily broken due to low elasticity thereof, the piezoelectronic device using the zinc oxide nanotubes may have low reliability and short life-span. Therefore, it is desirable to provide an improved piezoelectronic device to obviate the aforementioned problems such as easy fracture and short lifespan, and to improve the reliability of the piezoelectronic device.